Question 545923
83%=7/10 or 70% of your grade
x=3/10 or 30% of your grade
so 7/10+3/10=10/10 
and since your looking for a 70% you set equation = to 70 because that is the average you are looking for.
the reason i multiply 83 by 7 is because the average of {{{(83+83+83+83+83+83+83+83)/7=83}}} which is your given percentage, though your grades may be differentbut the result is same and for this purpose its just easier to calculate.


{{{(83(7)+x(3))/10=70}}}
{{{581+3x=700}}}
{{{3x=119}}}
{{{x=39.6667}}} for a 70%